What should I do for my dog?

Honestly, if there is nothing else the vet can do for her, the kindest thing you can do for her is to end her suffering. If the condition worsened in just a a few short days, it is not going to take long for her to get so bad to where she is really suffering. You need to think about her and what it means for her to be living with kidney failure. I would rather end my dog's life and end her pain than allow her to suffer. Dogs don't fear death and she will understand why you are doing it. You need to do what is best for her.